How commercial games handles on-the-fly font loading?

Question

This is how I handle font rendering in pseudocode(simplified):

FontFace* CreateFontFace(fontName, fontSize)
{
    FontFace* fontFace = LoadFromDiskCache(fontName, fontSize);
    if ( fontFace == 0 )
    {
        for(each glyph)
        {
            Load glyph using FreeType;
            Load its size and metric;
        }
        Pack all glyph bitmaps to a single UV-atlas
        {
            Calculate rectangles (RectangleBinPack); // Very slow!
            Blit glyphs to UV-atlas; // Slow!
            Insert rectangles to std::vector; // UV-dictionary;
            Insert metrics to std::vector;
        }
        Wrap it all to a struct FontFace;
        AddToDiskCache(fontName, fontSize); 
        // so on next startup it will be cached on HDD 
    }
    return fontFace;
}


bool OnInit(fontName, fontSize)
{
    for (each fontName)
    {
        for (each fontSize)
        {
            FontFace* fontFace = CreateFontFace(fontName, fontSize));
            Insert fontFace to container based on std::map;
        }
    }
}

void OnSomtimes(FontFace, pDevice)
{
    On demand create texture from FontFace.uvatlas on pDevice;
}

void OnRender(wstring, FontFace)
{
    if(needUpdate)
    {
        // Generate std::vector<Sprite> using given FontFace
        sprites = CreateSprites(wstring, FontFace);
    }

    Draw all vector<Sprite> at once with my SpriteBatch object; 
    // Big dynamic VertexBuffer, Instancing or GeometryShader 
    // depending on hardware caps
}

So I can cache some most used fonts or even all ever used in-game fonts. But in some apps user can just pick another font/size/style that app never seen before on the fly and it applies instantly. Or for example, in some games user can replace "font.tff" file in game folder and game will use it on startup in many sizes/styles and every of thousands of Unicode chars without additional time consuming preloading. Miracle!

I need something like this - an on-the-fly font loading.

Of couse, I can load glyphs separately on demand, and render glyph-by-glyph, but that means no batching, thousants of Draw calls per frame and huge GPU bandwidth. Not sure its ok or not for OpenGL, but its no go for D3D11.

How do they do that in game studios? Maybe you know a different approach? I heard about rendering fonts as geometry, GPU-processing and complicated curves algorithms, but cannot find helpful info in google.

Any help will be appreciated!

score 2 · Answer 1 · edited Oct 26 '19 at 00:23

Font rendering in games is usually done from a bitmap that contains all glyphs generated at compile/offline time. You can use a bitmap font generator like AngelCode BMFont which is really easy to use and well suited for games, as It is supporting DXTx compressed bitmaps that are more GPU bandwidth friendly.

For high resolution Font, Alpha Texted Magnification technique is currently the preferred technique in games, mostly when rendering decals.

score 1 · Answer 2 · answered Oct 21 '12 at 12:42

1

Instead of doing it glyph-by-glyph, why not render the entire string all at once in software as a single bitmap, then just render it as a single texture? Since text usually doesn't change very frequently once it's initially displayed, you can render the string in question on-demand when it's first displayed, then keep the string's texture in the GPU until it goes offscreen.

answered Oct 21 '12 at 12:42

bdonlan

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Good idea! Probably this technique can render small and/or static strings of just picked font very fast. Its significantly reduces number of polys (1 string = 1 quad). But, with many strings and/or changing fast (for example if user opens fast scrolling game chat/console or will input a text in a field char-by-char) overall performance will be lower due to strings processing and device resources generation. – Ivan Aksamentov - Drop Oct 21 '12 at 14:49

score 1 · Answer 3 · answered Oct 21 '12 at 12:52

1

The obvious improvement is to not render all 50.000+ Unicode characters up front. Do you really need Chinese? Instead, make FontFace capable of blitting characters on the fly as needed, and initially blit just U+0020 - U+007E (ASCII).

A slightly smarter solution may be to render all characters from a script whenever you need the first. After all, if you need one Thai character, you'll probably need more of them. But this obviously requires some extra tables to group Unicode characters.

answered Oct 21 '12 at 12:52

MSalters

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Thanks for idea! At first look, splitting atlases to different locales and then sorting strings to batch per-locale will be not too difficult. I`ll think about it. But, even loading ASCII-only chars are too slow to do it on game running. So implementing on-the-fly custom fonts are still impossible. – Ivan Aksamentov - Drop Oct 21 '12 at 13:46

How commercial games handles on-the-fly font loading?

3 Answers3